One known sustained release technique for ingredients having a pharmacological action, for example, wound-healing promoters, antibacterial agents, anti-inflammatory agents, etc., that is, ingredients having an action to promote wound healing, an analgesic action, an action to lessen inflammation, an antibacterial action against harmful bacteria to living bodies, etc., is to blend such an ingredient into a tackifying base. A similar sustained release technique is a DDS (drug delivery system) technique which is widely used with ointments, pastes, liniments and lotions The basic concept of this technique is the blending of a medicament into a tackifying base, where the medicament diffuses through the base to reach the skin boundary. Then, distribution of the medicament from the base to the skin surface takes place, and the medicament is transferred into the living body by diffusion through the skin tissues to act on the target organ. This sustained medicament release principle is based on a technique wherein the desired diffusion rate of a medicament through the base is achieved by selecting a base composition and designing a diffusion promoter, etc. for the base composition. In the application phase, however, the diffusion rate is also temperature dependent and thus these techniques are not suitably applicable to moisture-rich sites.
As a medical tackifying composition with a sustained medicament releasability directed to the application to moisture-rich sites, Japanese Examined Patent Application Publication No. Sho 44-16676 teaches an oral patch material for oral treatment, which comprises a hydrophobic elastomer blended with a hydrophilic hydrocolloid, and also discloses that the patch material is suitable for application to moisture-rich diseased parts and can be kept in a tackified state for a long time as a skin-binding patch for stomas and dressing for wounds in addition to usage as oral treating patch materials. The disclosure further states that it is possible to blend a medicament into a tackifier containing a hydrocolloid ingredient.
U.S. Pat. No. 4,340,043 discloses an adhesive-coated sheet material for wound covering, which comprises 1 to 25% by weight of an antibacterial agent to kill bacteria in wounds and surrounding covered skin area, a metal salt; an antibiotic such as neomycin; chlorobexidine and its salts; a quaternary ammonium compound; idophor; silversulphadiazine; or the like, and further discloses that the required content of the antibacterial agent is preferably up to 15% in a finely divided form to give an antibacterial action.
U.S. Pat. No. 4,551,490 discloses a pressure sensitive adhesive composition for various medical applications, which is resistant to erosion by moisture and biological fluids, which comprises a blend of mineral oil, one or more polyisobutylenes, or mixtures of one or more polyisobutylenes and an elastomer such as butyl rubber, styrene radical or block type copolymers, water-soluble hydrocolloid gums, water-swellable cohesive strengthening agents, tackifiers, etc., and also discloses such an active ingredients as silver sulphadiazine, where other silver compounds may be contained in the pressure-sensitive adhesive composition as a bandage for burn wounds.
Japanese Unexamined Patent Application Publication No. Hei 2-147063 discloses an antibacterial tackifying composition, which comprises a tackifying mixture of a solid hydrophobic acryl-based tackifier, an antibacterially effective amount of silver sulphadiazine, and such an effective amount of internally cross-linked sodium carboxymethyl cellulose as to release the silver sulphadiazine from the tackifying mixture, and further discloses that incorporation of the internally cross-linked sodium carboxymethyl cellulose into the acryl-based tackifier can promote the antibacterial effect with a surprisingly small amount of silver sulphadiazine.
However, all the above-mentioned techniques are based on mere blending of a medicament in a tackifying composition as a base to obtain a sustained medicament releasability by adjusting the amount of a medicament to be mixed or changing the constitutions of the tackifying composition. An increased amount of the medicament to be mixed for strengthening the physiological action inevitably entails problems of medicament side effect and cost increase. Changing the constitutions of tackifying compositions also has a limit to combinations of medicaments to be used and applicability to moist sites.